1. Field of the Invention
The invention relates to the field of liquid handling apparatus. More particularly, the invention relates to the field of clinical diagnostic equipment. In still greater particularity, the invention relates to the field of clinical diagnostic equipment employing a sample handling apparatus. By way of further characterization, but not by way of limitation thereto, the invention is a detector for determining when an insufficient volume of a liquid has been delivered to an instrument.
2. Description of the Related Art
In the clinical diagnostics area, where samples of various body fluids are tested in order to diagnose various patient illnesses, accuracy is extremely important. Thus, serious problems can arise for a patient if the instrument analyzes a short sample. That is, if less than the expected volume of a bodily fluid such as serum, urine, sweat, cerebrospinal fluid or other sample fluids are injected into the instrument, inaccurate readings may result. Analysis of a short sample can thus cause improper diagnosis and improper medication to be prescribed.
In clinical diagnostic instruments a sample probe is generally utilized to withdraw a sample of liquid from a sample cup. Because most instruments are automated, there is no operator to determine whether the required volume of sample liquid has been withdrawn from the sample cup. In order to ensure that the desired volume of sample liquid had been withdrawn, prior devices have employed conductivity methods which use two or more probes. This method is expensive and complicated. Other devices attempt to determine sample volume with light sensors mounted on the sample probe. While suited for their intended purposes, these devices are expensive and, in many cases, inaccurate.